Safety valve



March 27, 1934. ACKERMANN SAFETY VALVE Filed Oct. 30, 1930 Patented Mar. 27, 1934 PATENT oric SAFETY VALVE Gottlieb Ackermann, Berlin, Germany Application October 30, 1930, Serial No. 492,320 In Great Britain September 16, 1930 4 Claims. (Cl. 137-53) The invention relates to safety valves for steam boilers and other pressure medium containers, of the kind in which a back pressure chamber in the valve casing is on the opening of the valve ..fil'1ed with the pressure medium, which'in the closing movement of the valve aids the closing force of the spring or other closing means.

In known high-lift safety valves the ingress and egress of the pressure medium to and from the back pressure chamber have been controlled by the main valve or by an auxiliary valve, the inlet and outlet of this chamber being simultaneously opened when the main valve lifted, so that the pressure medium could blow through the chamber without exerting any appreciable influence on the main valve, but as soon as the return movement of the main valve began in consequence of a fall of pressure in the boiler or the like, the outlet of the back pressure chamber was throttled and then completely closed, either before the pressure medium inlet into the said chamber was entirely'shut off by the main valve or simultaneously with'this action, and consequently a pressure was-produced in the chamber which assisted in closing the main valve. The high lift safety valve described in the specification of United States Patent No. 306,208 (Ashton and Gould) is base on this principle. This arrangement had the disadvantages that owing to the loss of pressure in the back pressure chamber due to its outlet being fully opened when the main valve lifted, the valve body struck sharply on the upper cover of the valve casing; and conversely, due to the progressive throttling or entire closure of the outlet of the said chamber during the closing stroke of the valve, the pressure in the chamber continuously increased and might result in forcing the valve violently against its seat, causing damage to the packing surfaces on a the valve body and valve seat. The construction according to Figure 10 of the United States patent specification No. 1,690,097 (Ackermann) was better in that the back pressure chamber was constantly relieved through a throttled opening, but even here the pressure in the chamber at the end of the closing stroke was considerable, due to the said opening being throttled, so that a satisfactory damping or checking of the movement of the valve was not ensured.

The chief object of this invention is to overcome these diiliculties.

According to the invention means are provided to ensure that the opening stroke of the valve is clamped by the compression of the contents of the back pressure chamber and that the pressure towards the end of the closing stroke is so regulated that the valve is returned to its seat without shock. The valve is so constructed that a reduction of the final pressure in the back pressure chamber takes place due to the throttling of an outlet opening, which is controlled by-a throttle device connected with the valve being so reduced that at the end of the closing movement the back pressure chamber is entirely or nearly free from excess pressure. I

In the accompanying drawing, various examples of construction of the high lift safety valve according to the invention are shown.

Figure 1 represents a valve in vertical longitudinal section, in the closed condition.

Figures 2 and 3 illustrate modifications in the shape of the valve guide and the adjacent sleeve.

The valve casing 1 (Figure 1) is connected by the socket 2 with the steam boiler or other pressuremedium container, 3 indicating the outlet leading to the atmosphere. The valve body 4 has a bell-shaped guide projection 5 which extends into a sleeve 6 of the'valve casing. Between the guide projection 5 and the sleeve 6, a narrow gap 24 may be provided, which serves as the inlet or the outlet to the back pressure chamber 7. In the case illustrated in Figure 1, it serves as inlet. In place of this gap, or in addition there-- to, narrow bores 8 may serve as inlet openings to the back pressure chamber 7. The sleeve 9 forms the outlet, and has a conical bore, in which the valve spindle 11 has a correspondingly formed enlargement 10. 12 indicates a spring plate, and 13 the valve spring.

When the permissible maximum pressure in the boiler is exceeded, the valve a lifts, then steam flows through the holes 8, or through the gap 24, or through both into the back pressure chamber '7. In the same degree as the valve 4 rises, the enlargement l0 throttles the conical bore in the sleeve 9 more and more, without, however, completely closing it at any time. As the inlet areas remain unthrottled, steam continues to flow into the chamber '7, in which, in

consequence of the throttling or damping acl tion, a higher pressure is produced. A hard blow of the bell-shaped guide projection 5 on the upper wall of the valve casing cannot take place, in consequence of the pressure existing in the chamber '7.

When the boiler pressure has fallen so far that the tension of the spring 13, combined with the pressure in the chamber '7 can force back the valve 4 on to its seat, then the conical enlargement 10 of the valve spindle 11 opens the outlet 4, and the guide sleeve 6, in an opposite sense,

since the upward or downward movement of the. valve 4 increases or throttles the gap 24. It will be seen that in the construction illustrated in Figure 2, as the valve 4 rises, the gap 24 is reduced in diameter so that the admission of pressure medium to the chamber 7 is throttled, while in the construction illustrated in Figure 3 the reverse action takes place, the gap 24becoming wider as the valve lifts.

What I claim and desire to secure by Letters Patent of the United States is:-- q

i. In high lift safety valve apparatus for steam boilers and similar pressure mediumcontainers, a casing forming a valve seat, a valve body,'a spring tending to close said valve body on said seat, a member movable with said valve body'and enclosing conjointly with said casing a counterpressure chamber, means to admit pressure medium to said chamber, said casing having a constantly open outlet to communicate said chamber with the atmosphere, a throttling device movable with said valve body, saidthrottling device being adapted to narrow said outlet progressively on the opening stroke of thevalve body and to increase the eifectivearea of said outlet on the closing stroke of the valve body, whereby the said member is prevented from striking forcibly against the top of the casing in said opening stroke and the valve body is prevented from striking forcibly against-the valve seat in the closing stroke.

2. In high lift safety valve apparatus for steam boilers and similar pressuremedium containers, a casing forming a valve seatra valve body provided with a bell shaped extension, a spring tending to close said body on said seat, said casing being provided with a sleeve partly enclosing said extension and spaced therefrom to admitpressure medium to a counter-pressure chamber enclosed by said sleeve and said extension, the-opposing surfaces of said sleeve and said extension being of conical form, whereby the area between them for admission of pressure medium to said chamber is rendered variable during movement of the valve body, said casing having a constantly open outlet to communicate said chamber with the atmosphere, at throttling device movable with said valve body, said throttling device being adapted to narrow said outlet progressively on the opening stroke of the valve body and to increase the effective area of said outlet on the closing stroke of the valve body.

3. In high lift safety valve apparatus for steam boilers and similar pressure medium containers, a casing forming a valve seat, a slightly conical sleeve on said casing, a valve body provided with asIig'htly conical extension enclosing conjointly with said sleeve a counter-pressure chamber, a spring tending to close said body on said seat, said body adjacent to the seating zone thereof being provided with, holes of invariable area to admit pressure medium to said counter-pressure chamber, said sleeve and said extension being slightly spaced apart and the gap between them providing an inlet and outlet passage of variable area communicating between said counter-pressure chamber and the interior of the casing, said casing having a constantly open outlet to commun'cate said chamber with the atmosphere, a throttling device movable with said-valve body, said throttling device being adapted to narrow said outlet progressively on the opening stroke of the valve body and to increase the effective area of said outlet on the closing stroke of the valve body.

4. In a safety valve, a casing comprising a valve seat and an exhaust port, said casing being provided with two internally conical sleeves, a valve body movable in said casing and having a plurality of projections to vary the effective outlet area of both of said sleeves, one of which projections conjointly with one of said internally conical sleeves on said casing encloses a counterpressure chamber, means to admit pressure medium to said chamber, said internally conical sleeve be'ng adapted to permit escape of pressure medium from said chamber to said exhaust port, the second of said internally conical sleeves being adapted topermit escape of pressure medium from said chamber directly to the atmosphere.

- GOTTLIEB ACKERMANN. 

